Previous techniques employed in pay television systems for encoding television channels so that they are unwatchable on standard TV receivers have involved the alteration of the video modulation or of the synchronizing pulses. The decoders furnished to the customers include circuits for restoring the video modulation and/or the synchronizing pulses to an approximation of their original form, but if this is to be done with precision, the circuits are so costly that compromise performance has been accepted. Other techniques employ an interfering carrier inserted at the midpoint of the video pass band of the TV channel so as to render the picture unwatchable. A channel that is scrambled in this manner is decoded at the subscriber's TV receiver by removing the interfering carrier with a narrow bandstop filter. The filter not only removes some of the video modulation, but it also causes changes in group delay of the video frequencies near the frequency of the interfering carrier. These effects are reduced by precorrecting the coded channel at the encoder, but because restoration of the missing video can never be realized, there is a loss in picture definition.